Anomalous structure in the single particle spectrum of the fractional quantum Hall effect

The single particle spectrum of a system reveals the energies of its quasiparticles; charged, long lived excitations. We measure the single particle spectrum of a 2D electron gas in the fractional quantum Hall regime. Despite the intensive study this system has received in the past, the structure of this spectrum is completely unexpected; the features we previously observed in the quantum Hall effect break up into a series of sharp features that disperse linearly in energy with density.